Neogene sedimentary deformation in the Chilean forearc and implications for Andean basin development, seismicity and uplift

Abstract

Neogene sediments in the northern Chilean forearc display a wide range of near syndepositional structures. Analysis of the origin and distribution of these structures in space and time offers new insights into the development of the forearc basins. The structures are described in detail and show many features associated with soft-sediment deformation, pseudo-diapirism and slope failure. Synsedimentary deformation reached a peak in the Late Miocene to Early Pliocene while the sediments were saturated in a largely plastic state, and many of the structures were probably triggered by seismic shock. Late-stage tilting of the forearc generated shear stresses in the sediments leading to slumping and sliding. Base-level revision and drainage incision led to sediment bypass and cessation of lacustrine sedimentation that was not necessarily linked to climate change. Compaction and dewatering of the basins caused transition of the sediments from a plastic to a brittle state. The age and distribution of structures associated with seismicity appears to correlate with increasing subduction erosion and westward drift of South America but not with basin subsidence, shortening rates or plate convergence. This suggests that upper crustal deformation is at least partly decoupled from plate movement.

Sedimentology and stable isotopes from a lacustrine-to-palustrine limestone deposited in an arid setting, climatic and tectonic factors: Miocene–Pliocene Opache Formation, Atacama Desert, Chile

“…6). However, as documented by Houston et al (2008), the Calama Basin experienced significant Miocene-Pliocene deformation, including tilting, fold dome formation, monocline and thrust faulting, and slumping.…”

Coastal staircase sequences reflecting sea-level oscillations and tectonic uplift during the Quaternary and Neogene

“…In an ascending order (increasing apparent uplift rate), the results from Table 1 Along convergent margins, the way in which forearc dynamics relates to the geometric and dynamic parameters of the subduction system remains poorly known. Uncertainties about the evolution of forearc areas underscore the fact that little or no straightforward relationships have been found between the deformation of forearc and plate kinematics (Hartley et al, 2000;Houston et al, 2008). Uplift and subsidence, erosion and detritical paroxysms poorly match changes in plate convergence both in time and space (Hartley et al, 2000;Houston et al, 2008).…”

“…Uncertainties about the evolution of forearc areas underscore the fact that little or no straightforward relationships have been found between the deformation of forearc and plate kinematics (Hartley et al, 2000;Houston et al, 2008). Uplift and subsidence, erosion and detritical paroxysms poorly match changes in plate convergence both in time and space (Hartley et al, 2000;Houston et al, 2008). Additional difficulties arise from the fact that several subduction-related processes may cause comparable rates of uplift or subsidence.…”

The tectonic regime along the Andes: Present‐day and Mesozoic regimes

“…The tectonic regime in the forearc will depend on the amount of crustal erosion by subduction, and could vary from moderate accretion to an extensional setting, in cases of robust crustal erosion (Houston et al 2008).…”

“…Local extensional features have been related to subduction erosion processes that lead to trench-ward gravitational collapse, forearc subsidence and extension that may not necessarily be directly linked to absolute motion under a high compressive regime and westward drift of the upper plate (von Huene and Ranero 2003;Houston et al 2008).…”